1. Field of the Invention
The present invention relates to a valve gear device for internal combustion engines which has a valve stopping mechanism for stopping or deactivating an intake or exhaust valve continuously.
2. Description of the Prior Art
As a conventional example of a valve gear device for internal combustion engines of this kind, Japanese Examined Patent Publication (KOKOKU) No. 5-36605 has been known. This conventional device comprises: a valve stem connected to an intake or exhaust valve for opening and closing an intake (exhaust) hole which opens in a combustion chamber of an engine; a cam which is provided on a cam shaft; and a valve deactivating mechanism which is provided between the cam and the valve stem and which can keep the intake or exhaust valve in the closed condition. This valve deactivating mechanism includes: a body which is provided in a cylinder head and which is provided slidably in the axial direction of the intake or exhaust valve; a body hole which is formed in the body and which has an axial center that is perpendicular to the axial center of a stem; and a plunger having a stem pull-in and pull-out hole which extends toward the direction of the axial center of the body hole and the stem. In this valve deactivating mechanism, when the oil pressure is applied to the plunger, the stem is engaged into the stem pull-in and pull-out hole of the plunger so that the plunger and the stem can be moved relative to each other. Therefore, even if the cam is rotated, the torque thereof is not transmitted to the stem so that the intake or exhaust valve is kept in the closed condition. When the oil pressure is not applied to the plunger, the plunger engages the stem, and the plunger and the stem are moved together. Therefore, together with the rotation of the cam, the intake or exhaust valve is opened or closed.
The above-mentioned conventional device has the following disadvantages: the stem of the plunger engaging with the stem pull-in and pull-out hole is accomplished by supplying oil pressure to one end portion of the plunger and displacing the plunger so as to intersect the axial center of the stem. However, the timing of this displacement is not considered. Accordingly, the function of the valve gear device itself may not be impaired, but the engagement of the stem into the stem pull-in and pull-out hole of the plunger may be delayed. At that moment, the stem may collide with the other portion so that some noise may be generated. Furthermore, in order to endure such a collision, the materials of the plunger and the stem should be selected from the materials having high durability, and consequently a higher cost.